A voltage measuring apparatus measures an output voltage of an assembled battery in which a plurality of unit cells are connected in series and are divided into a plurality of blocks. The apparatus includes: a block voltage detection section which detects a voltage of at least one of the plurality of blocks and provides an analog voltage signal; a reference power supply which generates a reference voltage; a sampling voltage generation section which generates a sampling voltage based on the reference voltage; a storage for storing voltage date corresponding to the sampling voltage; and an A/D conversion section of the block voltage detection section that digitizes the sampling voltage with the reference voltage for A/D conversion. A difference between the digitized sampling voltage and the voltage data is calculated and it is determined that abnormality occurs in the A/D conversion section when the difference is larger than a threshold.
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